The present invention relates generally to mechanisms for protecting mechanical drive components from overloads, and more particularly to a brake coupled between components of an agricultural disc mower that quickly stops rotation of a cutterhead in the event the cutterhead strikes an object with sufficient force to activate a shear mechanism, allowing the cutterhead to rotate freely.
Typical disc cutterbars used in agriculture include an elongated housing containing a train of meshed idler and drive spur gears, or a main power shaft coupled by respective bevel gear sets, for delivering power to respective drive shafts for cutterheads spaced along the length of the cutterbar. The cutterheads each comprise a cutting disc including diametrically opposed cutting blades (though configurations with three or more blades are known) and having a hub coupled to an upper end of a drive shaft, the lower end of the drive shaft carrying a spur gear in the case where a train of meshed spur gears is used for delivering power, and carrying a bevel gear of a given one of the bevel gear sets in the case where a main power shaft is used. In either case, bearings are used to support the various shafts. The cutterheads are rotated at a relatively fast speed making the drive components, such as gears, bearings and shafts, vulnerable to damage in the event that the unit strikes a foreign object. For background information on the typical structure and operation of some disc cutterbars, reference is made to U.S. Pat. No. 4, 815,262, issued to E. E. Koch and F. F. Voler, the descriptive portions thereof being incorporated herein in full by reference.
In order to minimize the extent of such possible damage to the drive components, it is known to incorporate a shear device somewhere in the drive of each unit which will xe2x80x9cfailxe2x80x9d upon a predetermined overload being imposed on the device. As used herein with reference to shear devices, the terms xe2x80x9cfailxe2x80x9d or xe2x80x9cfailingxe2x80x9d are intended to cover the actual function of such devices, i.e., shearing, fracturing, breaking and the like. Several such shear devices and arrangements are shown in U.S. Pat. Nos. 4,999,981, 4,497,161 and 5,715,662.
A serious drawback of prior art disc cutterbars is that, while they may incorporate a shear device to reduce or eliminate damage to the drive system in the event of an overload, they do not provide means or mechanisms to stop rotation of the cutterhead after failure of the shear device. With multiple cutterheads in line, generating overlapping cutting paths, rotating at high speed and operating in a timed relationship, it is inevitable that when one fails it will lose its timed relationship with adjacent cutterheads, resulting in impacts and damage among the cutterheads comprising the cutterbar. Such damage is often significant not only in repair costs due to parts and labor, but also in lost harvesting time. The instant invention is directed to a brake mechanism that will stop further rotation of the cutterhead after failure of a shear device, thus preventing the damages described.
Accordingly, one object of the present invention is to provide a brake in the mechanical drive train of a disc cutterbar that will not only stop the transfer of power along the drive train in the event of overload, but also stop rotation of the non-driven components before further damage can occur.
Another object of the present invention is to provide a brake and shear mechanism in the drive of a disc cutterbar that will not only cause the cessation of power transfer at a predetermined load, but will also stop the rotation of non-driven components within one rotation.
Yet another object of the present invention is to provide a disc cutterbar with multiple cutterheads, each comprising a drive shaft connected to a mounting hub via a shear mechanism. A novel brake mechanism is triggered upon failure of the shear mechanism, stopping rotation of the lower hub and cutterhead.
It is yet another object of this invention to provide an improved disc cutterbar that is relatively durable in construction, inexpensive of manufacture, carefree of maintenance, easy to assemble, simple and effective in use, and less likely than prior art cutterbars to sustain costly damage upon contact with a fixed object.
These and other objects, features and advantages are accomplished according to the instant invention by providing a disc cutterbar with at least one cutterhead having a two-piece mounting hub, one piece rotatably driven and the other supporting a knife for severing standing crop material, with an epoxy layer bonding the two pieces together and forming a shear device therebetween. A brake is associated with the knife-supporting piece whereby upon failure of said shear device, the knife-supporting piece is stopped from rotating within one revolution.